In several applications a Light Emitting Diode (LED), which emits blue light, is combined with luminescent material which converts a part of the blue light towards light of another color, for example, to yellow, orange or red light. Often, blue light is partially converted to the another color, because white light must be emitted by an assembly of the LED and the luminescent material. The amount and characteristics of the luminescent material is chosen such that a required amount of blue light is converted towards a specific amount the another color such that the combined emission of remaining blue light and the specific amount of the light of the another color combines to white light, which means, to a light with a color point which is close to the black body line in a color space.
For example, published patent application US2012/0001204 discloses a color adjusting arrangement wherein light emitters are combined with layers of luminescent materials to obtain a light emission of a specific color.
However, during production of lighting assemblies that use a combination of a blue light source and a layer of luminescent material which partially converts the blue light to light of another color a problem arises. It is relatively difficult to manufacture light emitters, for example LEDs, which all emit exactly the same blue light emission spectrum. It is not acceptable to combine light emitters, which slightly deviate from each other, with only one type of a layer with one specific amount of luminescent material, because it would result in lighting assemblies that emit slightly different colors of light. The emission of slightly different colors of light is well detectable by the human naked eye and may lead, for example, to luminaires with different light sources each emitting slightly different colors of light. A known solution is: each blue light emitter is characterized and binned, after manufacturing the blue light emitting light emitters, and each blue light emitter is combined with a layer with luminescent material of a certain thickness related to the characteristics of the specific blue light emitter to obtain a light emission that has the desired color point. Characterizing and binning the manufactured light emitters is relatively expensive, and a relatively large amount of different layers with luminescent material need to be kept in stock which is also relatively expensive.